# Problem: Your adventurous friend Lola goes bungee jumping. She leaps from a bridge that is 100 m above a river. Her bungee cord has an un-stretched length of 50 m and a spring constant k = 600 N/m. Lola has a mass of 48 kg. Lola stretches the bungee cord and it brings her to a stop. She then bounces back up again. What type(s) mechanical energy does the system (Lola and the bungee cord) have just before she jumps? (i.e., gravitational PE, elastic PE, kinetic energy, etc.)

###### FREE Expert Solution

Gravitational potential energy:

$\overline{){{\mathbf{U}}}_{{\mathbf{g}}}{\mathbf{=}}{\mathbf{m}}{\mathbf{g}}{\mathbf{h}}}$

Kinetic energy:

$\overline{){\mathbf{K}}{\mathbf{E}}{\mathbf{=}}\frac{\mathbf{1}}{\mathbf{2}}{\mathbf{m}}{{\mathbf{v}}}^{{\mathbf{2}}}}$

Elastic potential energy for a stretched cord/spring:

$\overline{){{\mathbf{U}}}_{{\mathbf{e}}}{\mathbf{=}}\frac{\mathbf{1}}{\mathbf{2}}{\mathbf{k}}{{\mathbf{x}}}^{{\mathbf{2}}}}$

The kinetic energy and gravitational potential energy of the system are mainly due to Lona's mass. The bungee cord provides the elastic potential energy of the system.

The system is stationary (v = 0). Thus, their kinetic energy is zero.

93% (409 ratings) ###### Problem Details

Your adventurous friend Lola goes bungee jumping. She leaps from a bridge that is 100 m above a river. Her bungee cord has an un-stretched length of 50 m and a spring constant k = 600 N/m. Lola has a mass of 48 kg.

Lola stretches the bungee cord and it brings her to a stop. She then bounces back up again. What type(s) mechanical energy does the system (Lola and the bungee cord) have just before she jumps? (i.e., gravitational PE, elastic PE, kinetic energy, etc.)